Connecting plug for an electric current supply rail

ABSTRACT

A connecting plug for an electric current supply rail, comprising a casing and contact fingers flexibly fastened in said casing. An operating device preferably in the shape of a plate is arranged in the casing and is slidingly displaceable along said contact fingers between an inoperative position where the contact fingers are withdrawn into the casing and an operative position where the contact fingers are pushed out to protrude from said casing.

United States Patent 1 Hyrlainen Feb; 12, 1974 CONNECTING PLUG FOR AN ELECTRIC CURRENT SUPPLY RAIL [75] Inventor; Mikko Aukusti Hyrlainen, Helsinki,

7 Finland [73] Assignee: Oy Nokia Ab, Helsinki, Finland [22] Filed: Sept. 1, 1972 [211 App]. No.: 285,853

[58] Field of Search339/l4 R, 14 L, 20, 21 R, 21 S,

3,688,240 8/1972 Routh et al. 339/21 R Primary Examiner-Marvin AdChampion Assistant Examiner-Robert A. Hafer Attorney, Agent, or Firm-Eric H. Waters et a1.

[ 5 7 ABSTRACT A connecting plug for an electric current supply rail, comprising a casing and contact fingers flexibly fastened in said casing. An operating device preferably in the shape of a plate is arranged in the casing and is slidingly displaceable along said contact fingers between an inoperative position where the contact fingers are withdrawn into the casing and an operative position where the contact fingers are pushed out to [56] References Cited protrude from said casing.

I UNITED STATES PATENTS 3,718,886 2/1973 Hoffmeister 339/21 R 3 Claims, 7 Drawing Figures I l Ill and CONNECTING PLUG FOR AN ELECTRIC 'CURRENT SUPPLY RAIL The object of this invention is a connecting plug for a current supply rail which consists of a support rail open along one side and longitudinal conductors fitted in the support rail, said connecting plug consisting of a casing-like body, contact fingers which are fixed at one end to the body and an operating device by means of which the fingers are moved from their withdrawn position inside the body to a position inwhich they protrude from the body in order to make contact with the said conductors or to attach the connecting plug to the support rail.

In earlier known types of connecting plugs, the operating device for moving the contact fingers consists of a number of eccentrics located on a common shaft (e.g., Finnish Pat. No. 44,019 and English Pat. No. 1,220,910). One disadvantage of this type of operating device is that it is complicated to manufacture, and, because of the space taken up by the eccentrics and their operating lever, it is difficult to locate the points of contact between the eccentrics and the contact fingers near the finger ends. Because of this the contact fingers, some of which act as gripping fingers, have too great a flexibility over their length between the contact points and the finger ends. Consequently too great a load, for example a heavy lamp, cannot be attached to the connecting plug without the risk of it coming loose from. the supply rail. Connecting plugs in which the operating device for the gripping fingers is a screw are also known (e.g., English. Pat. No. 1,000,925). In such devices, however, it is difficult to arrange the finger movements in a properly controlled order so that no electrical contact is made before the protective earthing has been. carried out.

The purpose of this invention is to provide a connecting plug which is easy to manufacture and which will, at the same time, fulfil the specified safety requirements and lock firmly onto the current supply rail.

The main characteristicsof a connecting plug in accordance with the invention, as defined at the beginning of this description are presented in claim 1.

One advantage of this invention is that the operating device for the contact fingers is very much simplified. It can, for example, be a fiat disc provided with apertures and grooves for the arms of the contact fingers. The contact fingers are moved to their outer position by pushing the operating device towards the supply rail. When the operating device is pulled away from the supply rail the contact fingers spring back to a position within the body because of their own flexibility. The casing-like body of the connecting plug can be so designed that the disc which acts as the operating device can be pushed right on to the supply rail. The support points of the contact fingers are then extremely close to the supply rail, and, practically speaking, they are flexible only over that section which is located within the supply rail. The movement of the contact fingers can easily be completely controlled in both directions by providing the disc, which comprises the operating device, with sufi'lciently small apertures or grooves for the contact fingers. There will thus be two supporting surfaces for each contact finger, one operating when the contact fingers are to be moved inwards. The arms of the contact fingers can be designed in such a manner that those contact fingers acting as gripping elements An outline of the invention is given in the following by a description of one embodiment of the invention, with reference to the attached drawings, of which:

FIGS. 1 and 2 are end and side views respectively of a connecting plug in accordance with the invention.

FIG. 3 is a cross-section along line III-III in FIG. 2 of the connecting plug inserted in a current supply rail.

FIG. 4 is a partial cross-section of the connecting plug along line IV-IV in FIG. 1.

FIG. 5 is a top view of the operating device.

FIGS. 6 and 7 illustrate the shape of the finger arms and the operation of the operating device in crosssections along lines VIVI and VIIVII respectively in FIG. 5.

FIGS. 1 and 2 show a casing-like body 1 of a connecting plug, made of insulating material, and an operating device 2 with the aid of which fingers 3, 3, 4, 5, 6 and 6' are moved from their withdrawn position inside the body to a position in which they protrude from the body. Both positions of the operating device are shown in FIG. 1, the position in which the fingers are in their inner position being denoted by broken lines. Aconnecting flex 7 is led from the plug 1 to the electric ap pliance, most lighting fixtures however being directly attached to the connecting plug without any flex. Flexible earthing contacts 13 and 13' are also shown in the Figures.

FIG. 3 shows the connecting plug inserted in a supply rail. The supply rail consists of currents conductors 9 and 10 attached to a plastic insulation and fastening strip 16 and an aluminium support rail 11 to which a copper conductor 12 for protective earthing is mangled. The figure also shows a cross-section of the connecting plug. Fingers 4 and 5 act as contact fingers and make contact with the current conductors 9 and 10 in the figure. Fingers 3, 3 and 6, 6' act as gripping fingers and grip the edges of the U-shaped support rail of the supply rail, holding the connecting plug locked in the supply rail. The casing-like body I is asymmetric as seen in FIG. 1 where it can be seen that projection 15 is shorter than projection 14. As shown in FIG. 3, projection l5 accommodates projecting element 8 attached to plastic fastening strip 16 and the connecting plug can only be completely inserted in the supply rail when it is turned this way, thus maintaining the correct polarity in the appliance. The contact fingers 4 and 5 are each fixed separately to a bar 17 inside the casinglike body 1, on which the contact points for the flex 7 are also located. The gripping fingers 3, 3', 6, 6', are also attached to bar 17. These latter fingers however need not be insulated from each-other, and for this reason they can be manufactured from one or two U- shaped pieces of some suitable sprung steel. Earthing contact finger 13 is also attached to bar 17 on which the corresponding contact for flex 7 is located.

FIG. 5 shows the operating device 2 perspectively from above. The operating device is a disc shaped element made of insulating material and provided with grooves l8, 19, 20 and 21. The side surfaces of these grooves form supporting surfaces for the gripping fingers 6, 3, 3' and 6. The element 2 also contains grooves 22 and 23 whose side surfaces form supporting surfaces for the contact fingers 4 and 5. In the structure shown, there are in fact two supporting surfaces for contact fingers 4 and 5 owing to the narrowness of grooves 22 and 23, the movement of contact fingers 4 and 5 thus being positively controlled in both directions.

A suitable shape for the arms 24 and'25 of the pair of gripping fingers 3, 6 is shown in more detail in FIG. 6. The operating device 2 is shown in the figure with the gripping fingers in their indrawn position. The gripping fingers always tend to spring to this inner position. The positions of operating device 2 and the gripping fingers 3, 6 when the latter are moved to their position outside the body are indicated by broken lines. This figure also shows the earthing contact finger 13 which makes contact with the earth wire 12 (FIG. 3) initially due to its own flexibility only. When the contact plug is fully inserted, in other words when the operating device 2 is in its upper position, the gripping fingers 3 and 3' press further against the earthing contact fingers 13 and 13' thus increasing the contact pressure of the earthing contact fingers, as appears from FIG. 3.

The corresponding operation of the pair of contact fingers 4,-5 is shown in FIG. 7, together with a suitable shape for the arms 26, 27 of these contact fingers. The operating device is shown with the contact fingers 4, 5 in their indrawn position within the body. The contact fingers always tend to spring to this inner position. The positions of the operating device 2 and the contact fingers 4, 5 when the latter are moved to their position outside the body are indicated by broken lines.

The drawings and their associated description are only intended to outline the idea of the invention. Different embodiments of the invention can in fact vary considerably within the patent claims.

I claim:.

1. An electrical connecting plug comprising, in combination,

a support rail open along one side;

a plurality of longitudinal conductors in said support rail;

a casing having a base member;

contact fingers having arms fixed to said base memher;

a movable operating member having an element within said casing and displaceable rectilinearly along the longitudinal axes of said arms of said fingers, said operating member having at least one support surface for each finger, said arms of said fingers being arranged so that the spacings between fingers located opposite to each other vary along their length between the point at which said arms of said fingers are secured to said base member and the ends of said fingers, when said fingers are in a retracted position within said body, said fingers being movable by said operating member into an extended position outside of said casing for contacting said conductors, the displacement of said operating member along said arms applying pressure against said arms by said support surface to force the ends of opposite pairs of fingers away from each other and toward each other when said fingers are displaced between retracted and extended positions by corresponding displacement of said operating member.

2. An electrical connecting plug as defined in claim 1, wherein said movable operating member has a discshaped slide with notches providing at least one supporting surface for each of said figures and allowing said slide to move slidingly along said arms of said fingers.

3. An electrical connecting plug as defined in claim 2, wherein the supporting surfaces of said slide are arranged so that when said slide is moved towards the ends of said fingers some of said supporting surfaces force the corresponding fingers toward each other while other supporting surfaces force the corresponding fingers away from each other. 

1. An electrical connecting plug comprising, in combination, a support rail open along one side; a plurality of longitudinal conductors in said support rail; a casing having a base member; contact fingers having arms fixed to said base member; a movable operating member having an element within said casing and displaceable rectilinearly along the longitudinal axes of said arms of said fingers, said operating member having at least one support surface for each finger, said arms of said fingers being arranged so that the spacings between fingers located opposite to each other vary along their length between the point at which said arms of said fingers are secured to said base member and the ends of said fingers, when said fingers are in a retracted position within said body, said fingers being movable by said operating member into an extended position outside of said casing for contacting said conductors, the displacement of said operating member along said arms applying pressure against said arms by said support surface to force the ends of opposite pairs of fingers away from each other and toward each other when said fingers are displaced between retracted and extended positions by corresponding displacement of said operating member.
 2. An electrical connecting plug as defined in claim 1, wherein said movable operating member has a disc-shaped slide with notches providing at least one supporting surface for each of said figures and allowing said slide to move slidingly along said arms of said fingers.
 3. An electrical connecting plug as defined in claim 2, wherein the supporting surfaces of said slide are arranged so that when said slide is moved towards the ends of said fingers some of said supporting surfaces force the corresponding fingers toward each other while other supporting surfaces force the corresponding fingers away from each other. 